1. Field of the Invention
In general, the present invention relates to the structure of toy tops and the manufacturing techniques used to manufacture toy tops. More particularly, the present invention relates to toys tops and similar rotating toys that having a rotational inertia that varies as a function of rotational speed.
2. Description of the Prior Art
Toy tops have been in existence for thousands of years. In the many years that tops have been in existence, they have been built in a countless number of styles, shapes and sizes. Regardless of the form of a top, all tops share certain common functional features. Tops have a central axis around which they spin. The center of gravity associated with the top passes through the central axis and the mass of the top is evenly distributed around the central axis. As the top is put into motion, the top spins about its central axis. Since the mass of the top is evenly distributed around the central axis, the top spins in a uniform manner, thereby enabling the top to be balanced at a point in line with the central axis. The top will spin in a stable manner until the rotational speed of the top falls below a certain threshold level. As the speed of the top decreases, its angular momentum decreases. Eventually, the presence of angular momentum is insufficient to overcome the forces of gravity and the top tips over.
All tops have a rotational inertia. Rotational inertia is a function of the mass of the top and the square of the distance of that mass from the central axis of rotation. As such, if two tops of the same mass are provided and one top is wider than the other, the wider top will have a larger rotational inertia than the narrower top. As rotational energy is applied to a top, the speed at which the top spins is a function of its rotational inertia. Wide tops will spin slower than narrow tops if the tops have the same mass and are spun with the same degree or rotational energy. This same principle explains why ice skaters spin faster when they draw their arms closer to their bodies. As a skater brings their arms closed to their body, their rotational inertia decreases and the speed of their rotation increases.
In recent years, top systems have been manufactured that include a series of graduated tops that can be stacked on top of one another when spinning. An early example of such a system is shown in U.S. Pat. No. 3,906,660 to Voth, entitled, Toy Top. Today, such systems typically include at least three different tops of different sizes and a spring activated launcher for spinning the tops. In such systems, each of the tops embodies a different rotational inertia since each of the tops is a different size. Furthermore, all of the tops in such systems are launched by the same spring mechanism. Accordingly, each of the tops is launched with the same initial rotational energy. However, since each of the tops has a different rotational inertia, each of the tops spins at a different speed.
When stacking spinning tops, the tops do not become stable until two contacting tops are spinning at the same rate of rotation. If two contacting tops are spinning at different rates of rotation, then the tops are rotating relative one another. This tends to make the tops wander in position and separate from one another. In prior art top systems that use multiple stacked tops, it is difficult to have all the tops spin at the same rate of rotation since each top is initially launched at a different rate of rotation. Consequently, it is difficult to stack the spinning tops in a stable configuration and have the tops remain stable for any significant amount of time. Furthermore, no top can be added to the stack that is not spinning or is spinning slowly because the non-spinning top would immediately destabilize the faster spinning tops and cause the stacked structure to fall.
A need therefore exists for an improved top structure that would enable the top to change its rotational inertia as a function of speed. Such an improved top structure would enable tops spinning at different speeds to quickly synchronize when stacked. Furthermore, stored angular momentum can be readily transferred to stationary tops or to slow moving tops when such tops are stacked on rotating tops. As such, a stationary top can be stacked upon moving tops without destabilizing the spinning structure. Such an improved top structure is provided below as defined by the following specification and claims.
The present invention is a toy top system that uses uniquely configured tops. The system contains a plurality of toy tops that can be stacked on top of one another while spinning. Each of the tops has a value of rotational inertia associated with it. At least some of the tops are configured to have a value for rotational inertia that varies as a function of the rotational speed of the top. The tops with a variable rotational inertia are capable of storing and releasing rotational energy while maintaining a near constant rate of rotation.
The tops with variable rotational inertias each contain free weights that are symmetrically disposed around its axis of rotation. The weights are biased toward the axis of rotation by a spring or by gravity. As the top spins, the weights move away from the axis of rotation against the counteracting bias. Since the mass of the weights moves away from the axis of rotation, the rotational inertia of the top changes and rotational energy is stored without altering the rate of rotation. The stored rotational energy is used to prolong the spinning time of the top and help different tops synchronize in speed when stacked.